1. Field of the Invention
The present invention relates to an improved socket assembly for use with an integrated circuit device or package (IC), having a socket which opens with force applied on the top edges of the socket to allow insertion or removal of the IC, and in one aspect to a socket for IC's having an improved positive contact opening structure.
2. Description of the Prior Art
Top loading sockets for integrated circuit devices or packages (IC's) are known and are used to connect IC's to printed circuit boards for test or burn-in by automated operations, or for the functional application affording the replacement of the IC without subjecting other components on a printed circuit board or the like to heat, to afford the removal or replacement of the IC. To this end there have been sockets designed to afford the top-loading of the IC, whether the IC is leaded or leadless.
Examples of the sockets or carriers of the prior art include U.S. Pat. No. 4,491,377 directed to a carrier for a leadless chip and comprising a base portion, a support housing, a plurality of position contact pins and a spreader. The same are secured together by a plurality of studs. The spreader moves with respect to the remainder of the structure. Downward movement of the spreader, which has an inwardly and downwardly projecting lip which engages an edge of each pin to act as a camming surface against the edges of the pins, causes a bending of the pins to urge them outwardly from a central cavity defined by the contact pins to allow insertion of the leadless chip carrier into the cavity to a position to rest on the top surface of the intermediate support. Release of the downward pressure on the spreader will relax the contact pins, and they will engage the edges of the leadless chip carrier. This position of the contact pins places them in physical and electrical contact with the chip carrier and locks the chip carrier in the housing. This structure has a lip which engages the upper inwardly diverging edge of each contact pin and does not restrict the possible displacement of the free standing end of one or more of the contact pins. Each contact pin has an inclined surface which engages a substantial surface of the inwardly and downwardly inclined lip of the spreader, increasing the force to deflect the pins to the open position for receiving the chip carrier.
U.S. Pat. No. 4,846,704 disclosed a test socket having a main body supporting a plurality of flat plate-like contacts which face an installation recess. The contacts are fixed to the base in a fashion such that each lead leg may be extended downward and has an elastic curved part which is bent somewhat outward above the fixed part. At the upper end of the curved part is a contact part which is pressed against the IC chip by the elasticity of the curved part. A trigger part of the contact is positioned between the socket body and a cover and can be compressed downwardly by the lower edge of the cover to retract the contact part. This movement permits an IC chip to be inserted into a recess space defined by rows of the contacts. As above, the cover engages each contact trigger part to effect an elastic or resilient transformation of the curved part to retract the contact part and to release it against the lead of the chip.
Sockets of a similar design are found in U.S. Pat. Nos. 4,623,208; 4,715,823 and 4,846,703. These IC socket assemblies have contacts formed with a pressure receiving portion used to pull the contact portion away from the IC receiving cavity when a top or housing is moved vertically with respect to the base supporting the contacts. Again stability of the contact portion of each contact, together with positive flexure of the contact to retract the contact portion, is lacking in the structures disclosed, and contact between the top or housing with each contact is required.
Further, the structure of the sockets with a pressure receiving portion projecting from the contacts causes them to increase the profile or area the socket structure requires on the printed circuit board.
The socket assembly of the present invention affords positive movement of the contacting portion of the contact.
The contacts have a profile which affords a substantial reduction in the dimensions and area of the socket structure, and therefore the area required on the printed circuit board.
The retraction device to retract the contacting portion of the contacts restricts displacement of the contacting portion and assures positive movement of the contacting portion.
The socket assembly is of a design which reduces the number of dimensionally critical features on each part.